Design of semiconductor devices moves toward further high-speed and low-loss characteristics, which raises requirements of increased density and fineness of wiring in the circuit therein. The minimum wiring width currently required is several tens of nanometers. To satisfy such requirements, the aluminum alloy wiring has been substituted by copper wiring which has lower resistivity and more superior durability.
For example, there is a known technology of supplying metal atoms onto the surface of a substrate through the use of a physical method such as sputtering, thus forming a metal film on the substrate surface. Moreover, there is another known technology in which a liquid organic metal complex such as copper-hexafluoroacetylacetonato-trimethylvinylsilane is used as the raw material, which raw material is prepared in solid state, and then is dissolved in a solvent, followed by gasifying the raw material by utilizing a thermal reaction, thereby forming a copper film on a substrate.
Furthermore, there is a disclosed technology in which a gas made up of a halogen and a rare gas is supplied to a chamber to generate plasma of the gas and etch a target, thus forming a precursor being a compound of the metal existing in the target and the halogen, which precursor is then supplied onto the surface of a substrate to form a metal film thereon, (Patent Documents 1, 2, and the like).
Specifically in Patent Document 2, in conducting etching of a copper plate which is the material to be etched by using a Cl2 gas plasma, the adequate control of the relation between temperatures of the copper plate and the substrate generates Cu in a hole created in the substrate, thus forming a thin film of Cu therein. As for the relation between temperatures of the copper plate and the substrate, the temperature of copper plate as the material to be etched is set to a high level (for example, 300° C. to 400° C.), and the temperature of the substrate is set to a low level (for example, about 200° C.).
That is, according to Patent Document 2, Cl2 gas is supplied to the chamber and plasma is generated in the chamber, thus generating Cl radicals by the plasma dissociation reaction of the halogen gas. The generated Cl radicals cause the etching reaction with the copper plate which is the material to be etched to thereby generate CuCl vapor (containing also a polymer such as Cu3Cl3). When CuCl vapor and Cl radicals thus generated are supplied into the hole formed in the substrate, the reaction between the CuCl vapor and the Cl radicals forms Cu in the hole. By the deposition of the Cu, the Cu is buried in the hole.
In conducting the film-forming reaction of Cu in the hole, however, there occurs not only the film-forming reaction but also the etching reaction by the Cl radicals to the formed Cu film. Therefore, according to Patent Document 2, the amount of Cl radicals is controlled so that the Cu is buried in the hole, and an atmosphere is created in which the rate of the Cu film-forming reaction becomes slightly larger than that of the Cu etching reaction.    [Patent Document 1] Japanese Patent No. 3727878    [Patent Document 2] Japanese Patent No. 3653053